What are you lookin' at?

Yes, lady at the grocery store, I know that I stood in the card section and laughed out loud at the card I was reading. Okay, so I probably cackled, it was THAT funny. I know that I am in public and should use my inside voice, but a little courtesy would be nice. You don't have to look at me like I'm nuts. After all, when I walked past you 5 minutes ago in the pet food aisle and you were singing "you....are the sunshine of my liiiife" along with the overhead system and you pointed at me and gave a little wink, I just smiled back. It's polite not to pass judgement. Just smile and ignore the crazy.